Scetch error

This is my first ever 3d Printer it is a Geeetech Prusa I3 Pro W with a GT25560 card i keep getting the same error trying to verify. I have installed in the library the U8glib .zip, and the ArduinoBoardManager .zip, this is the error i get.

Build options changed, rebuilding all
In file included from sketch\MarlinConfig.h:34:0,

from C:\Users\D.Grover\Downloads\Marlin\Marlin\Marlin.ino:31:

sketch\pins.h:170:64: fatal error: pins_GT2560_REV_A.h: No such file or directory

#include "pins_GT2560_REV_A.h" // ATmega1280, ATmega2560

^

compilation terminated.

exit status 1
Error compiling for board Arduino/Genuino Mega or Mega 2560.

Looks like you are missing yet another library.

.

You may get better help on the RepRap Forum which is devoted to 3D printing.

...R